1. Field of the Invention
The present invention relates generally to a compressor for use in cooling, refrigeration or air-conditioning, and more particularly to a compressor which has an improved structure for coupling a pipe to a casing of the compressor. Further, the present invention relates to a method of assembling of the compressor which has an improved technique for coupling a pipe to a casing of the compressor.
2. Description of the Related Art
A compressor is constructed such that a compressor unit and an electric motor are housed in a hermetic casing. The compressor is equipped with pipes for respectively sucking or discharging refrigerants or coolants to or from other devices, e.g., evaporaters.
In a conventional compressor, there are various ways of coupling a discharging pipe or suction pipe, etc. to a compressor casing. For example, an aperture is formed in a side wall of a compressor casing and an iron joint to which a pipe may be fixed by brazing is fixed in the aperture by welding. If copper is used as the brazing material, there is a problem of embrittlement of the iron joint because of the effects of phosphorus contained in the brazing material and so silver brazing material is typically used. However, silver brazing material is costly, in addition to which automation is difficult since flux is needed during brazing and the flux has to be removed in a subsequent stage. Also, there is a lack of reliability with resistance welding, as the iron joints are liable to rust during storage.
Resistance welding or ring projection welding is practiced by flowing an electric current to a resistive contact portion between members to be welded together. The current flowing in the resistive contact portion generates a large quantity of heat which melts the contact portion. A heat quantity Q in resistance welding is given by a following equation: EQU Q=0.24.multidot.I.sup.2 .multidot.R.multidot.t
where I is a current, R is a resistance at the contact portion including internal resistances of both members to be welded together and t is a time the current flows.
The above described resistance welding is practiced for the contact portion between the casing and the iron joint by pressing electrodes of a resistance welding machine against the casing and the pipe.